I think it might be the client version that's causing the problem.
4.1.1.0 introduced a fix for Bug 592 [0], but, in doing so, broke other
things related to Kerberos, as reported in Bug 1258 [1] and (hopefully)
fixed in 4.1.2.0.

Yes, updating to 4.1.2.1 through the PPA fixed it. Working perfectly with Kerberos now.

Thank you so much for the aid, Stefan.

Regards,
Rubens